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A-Level Biology COPY > M6, C23 Ecosystems > Flashcards

M6, C23 Ecosystems Flashcards

1
Q

define ecosystem

A

all the organisms living in a certain area and all the non-living conditions found there

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2
Q

what are biotic factors

A

The living features of an ecosystem

eg. predators or food

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3
Q

what are abiotic factors

A

The non-living features of an ecosystem.

eg. temperature, rainfall, pH, soil nutrient availability

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4
Q

define habitat

A

the place where an organism lives within an ecosystem

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5
Q

How does light intensity affect an ecosystem

A

It affects the growth of producers.

Determines the rate of photosynthesis in plants.

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6
Q

how does temperature affect an ecosystem

A

affect the growth of producers (rate of photosynthesis)

could provide better/worse living conditions for organisms

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7
Q

why do we say that ecosystems are dynamic systems

A

the biotic and abiotic factors are always changing

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8
Q

how does water availability affect an ecosystem

A

affects photosynthesis in plants (producers)

water organisms need a plentiful supply of water to survive

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9
Q

how does oxygen availability affect an ecosystem

A

needed for respiration in organisms

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10
Q

how does soil type affect an ecosystem

A

certain plants will grow in certain pH of soil (producers)

needs to be soft enough to allow plants to grow

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11
Q

define trophic level

A

a stage in a food chain that’s occupied by a particular group of organisms

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12
Q

define producer

A

an organism that produces organic molecules using sunlight energy (plants)

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13
Q

define consumer

A

an organism that eats other organisms

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14
Q

draw a simple food chain

A

oak tree -> caterpillar -> starling -> cat

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15
Q

define biomass

A

dry mass of living material

producers store energy as biomass

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16
Q

Explain why biomass decreases at each level in a food chain

A

Energy is lost from an organism because…

  • not all of an organism may be eaten,
  • parts of an organism may be indigestible,
  • some energy is transferred to the environment through metabolic heat,
  • some energy is lost through excretion
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17
Q

give some examples of how human activities have improved ecosystems and the transfer of biomass

A

Herbicides - kill weeds that compete with agricultural crops for energy, grow faster, increasing productivity

Fungicides - kill fungal infections that damage agricultural crops

Insecticides - kill insect pests that eat and damage crops, less biomass is lost

Fertilisers - provide crops with minerals, increases efficiency of energy conversion

Rearing livestock involves controlling the conditions so more energy is used for growth, more biomass produced.

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18
Q

define decomposer

A

organisms that consume organic material (roots, bones)

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19
Q

define detritivores

A

an animal which feeds on dead organic material

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20
Q

define saprotroth

A

an organism that feeds on decaying organic matter

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21
Q

what do pyramids of biomass show

A

the total dry mass of all organism at each trophic level at a given time
The area of the bar is proportional to the dry mass of all the organisms at that trophic level

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22
Q

how could measure the amount of biomass in a material

A

Easiest way is to measure mass of fresh material
Water content in organisms must be removed

Organism heated in an oven at 80ºC until all the water has evaporated
Dry organism weighed to measure mass in grams
The figure is multiplied by the number of organisms present in a given area

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23
Q

what is the role of photosynthesis in the carbon cycle

A

carbon is absorbed by plants when they carry out photosynthesis
it becomes carbon compounds in plant tissues
this is passed onto primary consumers when they eat plants and then onto secondary and tertiary consumers

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24
Q

what is the role of decomposition in the carbon cycle

A

decomposers secrete enzymes which break down the carbon compounds in dead organic material
they then absorb the products of digestion for use in respiration

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25
Q

what is the role of respiration in the carbon cycle

A

carbon is returned to the air as all living organisms carry out respiration which produces carbon dioxide

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26
Q

what is the role of combustion in the carbon cycle

A

if dead organic matter ends up in places where there aren’t any decomposers (oceans/bogs), its carbon compounds can be turned into fossil fuels over millions of years
the carbon is released when they’re burnt

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27
Q

what is the role of volcanoes in the carbon cycle

A

rocks can be formed from dead organic matter (coal, limestone and chalk)
carbon can be returned to the atmosphere by the rocks being drawn deep into the Earth’s crust by the movement of tectonic plates
they undergo chemical changes and release carbon dioxide which is returned to the atmosphere by volcanoes

28
Q

what is the role of weathering in the carbon cycle

A

the carbon-compound rocks can become land which is weathered
the rain can do this as it’s slightly acidic or physically by plant roots and animals
chemical weathering causes mineral ions and bicarbonate ions to be released from the rock into solution and enter ground water from where they’re transported into rivers and oceans
they combine with carbon-containing compounds like limestone

29
Q

what is the role of oceans in the carbon cycle

A

carbon dioxide can directly dissolve into the oceans and be transported deep underwater by currents
carbon dioxide can remain in these slow moving currents for hundreds of years before returning to the surface and being released back into the atmosphere

30
Q

define succession

A

the process by which an ecosystem changes over time

31
Q

what’s the difference between primary and secondary succession

A

primary succession happens on land that’s been newly formed or exposed. there’s no soil or organic material

secondary succession happens on land that’s been cleared of all the plants but soil remains

32
Q

what are pioneer species

A

the first species to colonise the area

specialised to cope with harsh environments

(seeds and spores are blown in by the wind and begin to grow)

33
Q

describe the process of primary succession

A

1) Seeds and spores are blown in by the wind and begin to grow (pioneer species).
2) The abiotic conditions are harsh (no soil to retain water) but the pioneer species change the abiotic conditions - they die and microorganisms decompose the organic material and form soil.
3) Conditions are now less hostile and new organisms move in and grow. They add more organic material when they die, the soil becomes richer in minerals.
4) Larger plants can then grow, making more habitats so animals can move in.

34
Q

define climax community

A

the final stage of succession where the ecosystem is supporting the largest and most complex community of plants and animals it can
it’s in a steady state

35
Q

define plagioclimax

A

where humans have prevented an ecosystem developing and further
(eg. deforestation)

36
Q

what’s the difference between abundance and distribution

A

Abundance is the number of one species in a particular area.

Distribution is where a particular species is within the area you’re investigating.

37
Q

draw a pyramid of numbers for this food chain:

grass -> rabbit -> fox -> fleas

A

the bottom level is the largest then it gets smaller for rabbits and smaller for foxes.
the top level is then large as well because it takes a lot of fleas to consume one fox

(the pyramid of biomass however, would look like a normal pyramid)

38
Q

what do pyramids of energy show

what are the units used

A

Pyramids of energy show the amount of energy available to the next trophic level.
Energy is measured in kilojoules per square metre per year, so seasonal anomalies will not show.

39
Q

define ecological efficiency

A

The efficiency with which biomass or energy is transferred from one trophic level to the next

40
Q

define gross production (in terms of food chains)

A

Total solar energy that plants convert to organic matter/absorbed or energy taken in

41
Q

define net production (in terms of food chains)

A

Energy available to the next trophic level

42
Q

why does the majority of the available energy to organisms not get taken in

A

Plants can’t use all light energy = wrong wavelength, some light is reflected, some light passes straight through leaf

Not all light can be used as it hits bark

Some parts of food e.g. roots/bones aren’t eaten (energy passes to decomposers)

some parts of food are indigestible so come out as waste/faeces (passes to decomposers)

43
Q

define respiratory loss

A

energy lost to the environment when organisms use energy produced from respiration for movement or body heat

44
Q

what equations can you use for net production and gross production

A

Net production = gross production – respiratory losses

Gross production = energy available – energy not taken in

45
Q

what equation can you use for the efficiency of energy transfer between trophic levels in a food chain

A

% efficiency of energy transfer or ecological efficiency = (net productivity of trophic level / net productivity of previous trophic level) X100

46
Q

how do calculate the efficiency of biomass transfer

A

first calculate the biomass consumed:
biomass consumed = mass (per m^2) x area of land

then:
% efficiency of energy transfer or ecological efficiency = (net productivity of trophic level / net productivity of previous trophic level) X100

47
Q

what happens after primary succession in order to create a climax community

A
  • At each stage, plants/animals better adapted out compete those already there, becoming the dominant species
  • Ecosystem becomes more complex
  • Creates more habitats, increases species diversity
  • Eventually a climax community is reached – it won’t change much after this
48
Q

define deflected succession

A

When succession is prevented by human activity, but the plagioclimax that develops is different to the normal course of the natural environment.

49
Q

why is random sampling done

A

Ensures the sample isn’t biased

Ensures any variation observed in the sample isn’t just due to chance

50
Q

write a method of how you can take a random sample on a field

A

Mark out a grid on the grass using 2 tape measures laid at right angles
Use random numbers to determine the x and y coordinates
Take a sample at each coordinated pairs

OR

Divide the field into a grid
Use a random number and letter generator to select the coordinates
Take samples at the coordinates

51
Q

what are the differences between line, belt and interrupted transects

A

Line transect – species that touch the tape measure are recorded

Belt transect – using a quadrat, they are placed next to each other

Interrupted transects – measurements are taken at intervals, e.g. by placing a point quadrat at right angles to the direction of the transect e.g. every 2m

52
Q

how do frame quadrats work

A
  • placed on the ground at random points within the area you’re investigating
  • the number of individuals of each species is recorded in each quadrat
  • the percentage cover can also be measured by counting how much of the quadrat is covered by the species (count a square if it’s more than half covered)
53
Q

how do point quadrats work

A
  • this is a horizontal bar on 2 legs with a series of holes at set intervals along its length
  • place on the ground at random points
  • pins are dropped through the holes and every plants the pin touches is recorded
  • the number of individuals if each species is recorded in each quadrat
  • percentage cover can be calculated by counting the number of times a pin has touched a species and dividing by the total number of pins dropped
54
Q

why does the abundance of a species change daily

A

Immigration
Emigration
Births
Deaths

55
Q

how can you estimate the number of organisms in a population

A

Estimated number in population = number of individuals in sample / area of sample

56
Q

what is the capture-mark-release-recapture technique

A

A sample of animals is captured, counted and marked in some way.
They are then released and allowed to remix with the population.
A second sample is taken later.
The population can be estimated from the proportion of marked animals in the second sample.

57
Q

what are the limitations of the capture-mark-release-recapture technique

A
  • the population always changes (could be a mass migration between taking the samples) and you’re assuming there are no deaths or births
  • not all organisms could have an equal chance of being captured (mother’s and their young will be more timid)
  • marks could be lost or could make the animal more noticeable to predators
58
Q

draw the carbon cycle

A

look it up

59
Q

draw the nitrogen cycle

A

look it up

60
Q

what is the role of nitrogen fixation in the nitrogen cycle

what are the bacteria involved

A

Nitrogen fixation is when nitrogen gas in the atmosphere is converted to ammonia by bacteria such as Rhizobium and Azotobacter. The ammonia can be used by plants.

Rhizobium are found inside root nodules of leguminous plants. They form a multualisitic relationship with the plants (provide the plant with nitrogen compounds and the plant provides them with carbohydrates).

Azotobacter are found living in the soil.

61
Q

what is the role of ammonification in the nitrogen cycle

A

Ammonification is when nitrogen compounds from dead organisms are turned into ammonia by decomposers, which goes on to form ammonium ions. Animal waste also contains nitrogen compounds - these are also turned into ammonia by decomposers and go on to form ammonium ions.

62
Q

what is the role of nitrification in the nitrogen cycle

name the bacteria involved

A

nitrification is when ammonium ions in the soil are changed into nitrogen compounds that can be used by plants (nitrates)
first nitrifying bacteria called Nitrosomonas change ammonium ions into nitrites
then other nitrifying bacteria called Nitrobacter change nitrites into nitrates

63
Q

what is the role of denitrification in the nitrogen cycle

A

denitrifcation is when nitrates in the soil are converted into nitrogen gas by denitrifying bacteria - they use nitrates in the soil to carry out respiration and produce nitrogen gas
this happens under anaerobic conditions (no oxygen), eg. in waterlogged soils

64
Q

Other than nitrogen fixation, how can nitrogen enter an ecosystem

A

Lightning

Haber process - making artificial fertilisers

65
Q

what are the bacteria responsible for these processes in the nitrogen cycle:

a) Nitrogen fixation
b) Ammonification
c) Nitrification
d) Denitrification

A

Nitrogen fixation - Rhizobium and Azotobacter

Ammonification - Decomposers

Nitrification - Nitrosomonas and Nitrobacter

Denitrification - Denitrifying bacteria

A-Level Biology COPY (23 decks)

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